For patients with localized breast, lung, and prostate cancer, several new treatment options have been developed in recent years. As care options expand, clinicians, patients, and policy-makers encounter difficult decisions. Despite the hope of superior efficacy against cancer, decreased side effects, or both generated by newer radiation modalities, it is unclear whether these new, expensive therapies will have an impact on patient health that is commensurate with their cost. A new approach is needed for evaluating diffusion of treatments while evidence of efficacy is still in development: evaluating utilization and costs according to likelihood of benefit. Some older patients with a higher burden of comorbidity will receive less benefit, and perhaps greater risk with more aggressive therapy. We propose a population based study of older persons with breast, lung, or prostate cancer enrolled in the Medicare fee-for-service program, in order to address the following aims with a particular emphasis on complex patients: Aim 1: To identify, as a function of clinical factors among patients diagnosed in 1996-2005, changes in the proportion of patients treated with newer radiation modalities as well as in over-all treatment approaches. We will also examine whether the use of new treatment modalities is associated with increases in the percentage of patients receiving cancer therapy; Aim 2: To identify factors associated with adoption of new radiation modalities including provider, health system, and non-clinical patient factors; Aim 3: To determine the total costs to the Medicare fee for service program for initial care of breast, lung, and prostate cancer in 2006-08 and the proportion of these costs that are associated with radiation modalities; Aim 4: To compare the effectiveness of radiation treatment modalities. This retrospective, longitudinal study will use population-based data obtained from the Center for Medicare and Medicaid Services (CMS) and the National Cancer Institute. This SEER-Medicare database will be used to delineate changes in cancer therapy according to cancer and comorbidity strata for patients diagnosed through 2005. We will also obtain a 100% sample of Medicare fee-for-service beneficiaries with breast, lung, or prostate cancer during 2006-2008, providing a comprehensive and timely assessment of cancer care, costs, and comparative outcomes. An experienced study team will conduct a methodologically rigorous analysis that includes multilevel, hierarchical modeling to account for clustering of patients at the physician and geographic level. Prior assessments of cancer care have not incorporated both cancer and comorbidity status into a comprehensive assessment of likelihood of benefit of cancer therapy. Addressing these knowledge gaps is critical for understanding the patient and health-system factors that affect the adoption of these technologies, as well as the implications for costs and outcomes - providing potential targets for intervention to improve the effectiveness and efficiency of treatment strategies. PUBLIC HEALTH RELEVANCE: New and expensive radiation therapies are frequently being used to treat older persons with cancers of the lung, prostate or breast. However, little is known about the risks and benefits of these therapies, their costs, or factors associated with their use. The proposed study, using data from both National Cancer Institute as well as Center for Medicare and Medicaid Services, will examine new radiation therapy modalities among Medicare beneficiaries as a function of health status, in an effort to improve decision making about cancer treatments.